To be honest I don't remember osso-notes, as I've never been a big user of notes applications. But there are several on SFOS, including one supporting Markdown, a terminal one, and another supporting encryption, as well as good text editors mimicking IDE with project (hence multiple files) support.

What you might miss from Maemo, particularly for notes, is widgets, but with SFOS you can leave the app open and have its thumbnail show information (at least some apps will show information on the cover, see screenshots of Foil Notes for instance).